In molds for injection molding of plastic articles, in addition to the typical mating mold parts, laterally moving slides are commonly used to move one or more core parts as the mold is opened and closed. When such a slide is employed the mold uses angle pins, sometimes known as horn pins, which are fixed at an angle to one of the mold parts and pass through a corresponding angular bore in the slide. When the mold is opened, the angle of the angle pin moves the slide laterally away from the part to remove the core element from the molded piece so that the molded piece can be ejected from the mold. This procedure is then reversed and the angle pin moves the slide to position the core element for molding of the next plastic article.
In using such molds, it is important that the slide be held in place when the mold is opening since usually the mold parts are separated sufficiently so that the angle pin is completely withdrawn from its corresponding angular bore in the slide. If the slide is not held by some other means, after the mold parts are fully separated, the slide can inadvertently become displaced, inhibiting closing of the mold without manual realignment of the slide and possibly causing damage to the mold or slide. Although the slides must be firmly and accurately held in the open position, the slides must also release readily when the angle pins reengage the angular inclined bores in the slides to move the core parts laterally together until the mold is again closed.
A number of devices have been used in the past to hold slides in their open position. Such devices are set forth in U.S. Pat. Nos. 3,811,645; 4,515,342 and 4,765,585. In U.S. Pat. No. 3,811,645 two types of slide retainers are disclosed. One is a cumbersome retainer identified as prior art that is attached to the mold and extends outwardly from the mold body and the other is an internal slide retainer with a pin that is attached to the slide. U.S. Pat. No. 4,515,342 discloses slide retainers that use a resilient arm that has a laterally projecting portion that engages the slide or an attachment to the slide. U.S. Pat. No. 4,765,585 discloses a spring loaded plunger with a projecting V-shaped head portion that engages the slide.
Unfortunately, these previous slide retainers are not entirely satisfactory. The slide retainers disclosed in U.S. Pat. Nos. 4,515,842 and 4,765,585 can be adversely affected by wear and by the tolerences in the mold apparatus. These devices also may not positively engage the slide and hence are to at least some extent unreliable. The prior art device in U.S. Pat. No. 3,811,645 takes up a lot of space and depending on required travel extends from the mold where it could interfere with the molding machine. Pressure is also exerted to the sliding parts during the entire movement of the slide retainer which is undesireable. The internal slide retainer set forth in U.S. Pat. No. 3,811,645 is a definite improvement over this prior art retainer and it also is more positive and reliable than the slide retainers in U.S. Pat. Nos. 4,515,842 and 4,765,585. However, the slide retainer set forth in this patent still has disadvantages. These disadvantages include the fact that jaws of the slide retainer are under a certain degree of spring force even when the slide retainer is not in use and the spring is also exposed to dirt and the like when the slide retainer is in use.
The novel retainer invention overcomes these problems associated with previous slide retainers. This retainer invention is positive in its action and is effective to secure a slide in its open position. With this invention the retainer has provision for surrounding all portions of its spring to keep it free from dirt, debris and the like. The retainer has provisions for making it easy to assemble and the jaws of the retainer are only under spring force when the retainer is in actual use to engage a pin that is in turn connected to a slide in the mold.